A next generation PHS (Next Generation Personal Handy-phone System) is a mobile communication system which realizes high speed communication, using a TDMA/TDD (Time Division Multiple Access/Time Division Duplex) system and an OFDMA (Orthogonal Frequency Division Multiple Access) system. A radio communication interface of the next generation PHS is disclosed in the non-patent document 1 mentioned below.
FIG. 9 is a diagram showing a outgoing call sequence of the next generation PHS. As shown in the diagram, a base station regularly sends a broadcast control channel (BCCH) including the base station ID of its own station, transmission power control information (a negative value indicating the difference between an actual transmission power and the base station maximum transmission power), and so forth (S200). Meanwhile, a mobile station establishes frame synchronization in the downlink direction (the direction from the base station to the mobile station), based on the broadcast control channel (S202), and then sends a timing correct channel (TCCH) corresponding to an uplink synchronous burst signal to the base station (S204).
Having received the timing correct channel from the mobile station, the base station calculates the difference between the receive timing and a desired receive timing of the timing correct channel to use as a timing correct amount (S206). Then, one communication channel for ANCH (Anchor Channel) to be allocated to the mobile station is determined (S208). Note that, in the next generation PHS, each communication channel is composed of a combination of a time slot according to the TDMA (e.g., a time slot length 625 μs) and a subchannel according to the OFDMA, and referred to as a PRU (Physical Resource Unit).
The base station calculates the difference between the received power and a desired receive power of the timing correct channel to use as a correct amount of the transmission power of the mobile station (S210), and sends to the mobile station a signaling control channel (downlink SCCH) containing the timing correct amount calculated at S206, the PRU for ANCH, determined at S208, and the correct amount of the transmission power of the mobile station, calculated at S210 (S212).
Having received the signaling control channel from the base station, the mobile station obtains the PRU for ANCH from the received signaling control channel (S214). Then, the mobile station corrects the transmission power of the ANCH, based on the transmission power correct amount contained in the signaling control channel (S216), and also corrects the transmission timing, based on the timing correct amount contained in the signaling control channel, whereby frame synchronization in the uplink direction (the direction from the mobile station to the base station) is established (S218). Further, the mobile station sends an uplink ANCH to the base station, using the PRU for ANCH obtained at S214, with the transmission power corrected at S216 at the transmission timing corrected at S218 to request allocation of PRUs for EXCH (Extra Channel) (S220).
Having received the uplink ANCH from the mobile station, the base station determines PRUs for EXCH composed of one or more PRUs (S222), and sends a downlink ANCH containing the determined PRUs for EXCH to the mobile station (S224).
Note that, in the next generation PHS employing the OFDMA system, receive timing difference and received power difference among uplink signals sent from respective mobile stations cannot be individually corrected in the base station. Therefore, the transmission timing of an uplink signal is corrected in a mobile station, as described above, to prevent inter-symbol interference (ISI). Moreover, an appropriate transmission power is set for a mobile station to prevent interference with an adjacent cell.
[Related Document]
    Non-Patent Document 1: “ARIB STD-T95 ‘OFDMA/TDMA TDD Broadband Wireless Access System (Next Generation PHS) ARIB STANDARD’, Ver. 1.0”, Dec. 12, 2007, Association of Radio Industries and Business